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Sex-linked Traits

Sex-linked Traits. Ch. 10.5. Sex chromosomes. Humans- 23 rd pair of chromosomes- X,Y Eggs- Have an X chromosome. Sperm- Half have an X chromosome, half have a Y chromosome. Fathers determine gender(sex) of offspring. Males- XY Females- XX 50% chance of having a girl or boy offpring.

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Sex-linked Traits

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  1. Sex-linked Traits Ch. 10.5

  2. Sex chromosomes • Humans- 23rd pair of chromosomes- X,Y • Eggs- Have an X chromosome. • Sperm- Half have an X chromosome, half have a Y chromosome. • Fathers determine gender(sex) of offspring. • Males- XY • Females- XX • 50% chance of having a girl or boy offpring.

  3. Sex-linked genes • Any gene on a sex chromosome- X or Y. • Majority are on X chromosome. • Examples- • Eye color in fruit flies- on the X chromosome • Red color is Normal and Dominant, XR • White color is Recessive. Xr • Females must have 2 recessive alleles to have white eyes. Xr Xr • Males need just 1 recessive allele ( they have only 1 X chromosome) Xr Y to have white eyes.

  4. Eye Color in Fruit flies

  5. Human X-linked recessive traits. • Hemophilia- bleeding disorder • Red-green color blindness. • more males with the disorder compared to females. • Females can be carriers- have one recessive allele- do not have the disorder, but can pass on the recessive allele to offspring. • Mothers pass trait on to sons. • Pedigree- Chart used to record and trace the occurrence of a trait in a family. • Squares- males • Circles- females. • Colored shapes- individuals that show the trait. • Parents are connected by horizontal lines(marriage line) • Children beneath them. • Generations – designated by Roman Numerals ( I, II, III etc) • Individuals are Numbered left to right in each generation.

  6. Sex-linked recessive pedigreeskips generations , see more often in males.

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